In most houses constructed after the 1920s, the external walls are made of two layers of brickwork (internal and outer) with a small air gap or cavity between them. Cavity wall insulation involves filling this gap with insulation material that reduces the amount of heat that can escape through the walls. To identify if your home is suitable for cavity wall insulation, look at pattern of the external brick work, see diagram below. You can also check whether you have cavity walls by measuring the depth of them at any entrance door or window of your property. Cavity walls are at least 26.5cm(10.5 inches) thick.  If you are unsure then call us or request a survey online and one of our surveyors will be happy to visit and take a look.